Which XML API?

Hello all,
I am developing a c++ (GUI) application that helps to publish the
photos/pictures on the web. I know there are lot of freewares available.
But I started doing this (1) to learn cross-platform GUI programming and
(2) all the applications that I worked with have predefined templates
for the output and it is not possible to modify the style. So I thought
of using XML/XSL to generate the output as desired by the user (in this
case by me).
Here is my question: Which XML/XSL parser API, I can use to develop? I
have been reading through Apache/Xpat/IBM parsers. I would like the
parsers API to be easy to learn, not blotting my executable, and free.
Any suggestions/links/ideas is appreciated.

Thank you in advance,
Joseph